1. Field of the Invention
The present invention relates to a power transmission chain and more particularly to a power transmission chain and a power transmission apparatus which are suitable for a continuously variable transmission (CVT) of a vehicle such as an automotive vehicle.
2. Related Art
As an automotive continuously variable transmission, there is known an automotive continuously variable transmission, as is shown in FIG. 7, including a drive pulley (2) having a fixed sheave (2a) and a movable sheave (2b) and provided on an engine side, a driven pulley (3) having a fixed sheave (3b) and a movable sheave (3a) and provided on a drive wheel side and an endless power transmission chain (1) placed to extend between the pulleys, wherein by moving the movable sheaves (2b), (3a) towards and away from the fixed sheaves (2a), (3b) by means of a hydraulic actuator so as to clamp the chain by virtue of hydraulic pressure, so that a contact load is generated between the pulleys (2), (3) and the chain (1) by the clamping force so as to transmit torque by a frictional force generated at the contact portions between the pulleys and the chain.
As the power transmission chain, JP-A-2006-242374 proposes a power transmission chain including a plurality of links each having front and rear insertion through holes through which pins are inserted to pass, and a plurality of first pins and a plurality of second pins which are arranged in a line for connecting together the links which are arranged in a chain width direction such that the front insertion through hole of one link is associated with the rear insertion through hole of another link, a longitudinal bending of the links being enabled through relative rolling contact movement of the first pins which are fixed in the front insertion through hole of one link and fitted movably in the rear insertion through hole of another link and the second pins which are fitted movably in the insertion through hole of one link and fixed in the rear insertion through hole of another link, and wherein to reduce noise by differentiating a biting timing of the pins into the pulley, two or more pin rolling contact surface shapes and pin contact positions with the pulley surface (which are offset in the radial direction of the chain) are used and the pins which are made to differ in the way described above are arranged at random.
In the power transmission chain which is made up of the links and pins, in a biting position where the pins shift from a straight line portion to a circular arc-like portion where the pins come into contact with the pulley, the tangential direction of the pulley and the traveling direction of the pins differ, and the pins are made to be brought into contact with the pulley while traveling downwards. Then, the pins staying in the straight line portion are also affected by the downward traveling motion of the pins in the biting position and are then caused to move vertically, and polygonal vibration is generated by the pins repeating the vertical movement. In addition, when the pins are disposed at equal intervals, by the pins coming into contact with the pulley in a constant cycle, a primary peak of collision frequency becomes large and causes uncomfortable noise to the ears.
In the power transmission chain disclosed in JP-A-2006-242374 above, by the basic configuration which reduces the polygonal vibration and random arrangement of the pins, the reduction in vibration and noise is realized. However, the approach of arranging the different types of pins at random to differentiate the biting timing of the pins into the pulley tends to increase the polygonal vibration, and it is difficult to make compatible the reduction in primary peak with the reduction in polygonal vibration by the random arrangement.